A parallelogram that does not have any right angles, but the sides are all
equal in length. Jones, 2
A triclinic mineral, Ca2 (Fe,Mg,Ti)6 (Si,Al)6 O (sub
20) ; aenigmatite group; in silica-undersaturated mafic to intermediate
rocks commonly as an alteration product of amphiboles; in Germany and the
Czech Republic.
Scot. Bituminous shale.
See:sanidine
The extrusive equivalent of granodiorite. The principal minerals, sodic
plagioclase, sanidine, quartz, and biotite or hornblende, commonly occur
as phenocrysts in a finely crystalline groundmass of alkali feldspar and
quartz. Accessory minerals are apatite and magnetite, and occasionally
augite. AGI
A group of extrusive igneous rocks, typically porphyritic and commonly
exhibiting flow texture, with phenocrysts of quartz and alkali feldspar in
a glassy to cryptocrystalline groundmass; also, any rock in that group;
the extrusive equivalent of granite. Rhyolite grades into rhyodacite with
decreasing alkali feldspar content and into trachyte with a decrease in
quartz. The term was coined in 1860 by Baron von Richthofen (grandfather
of the World War I aviator). Etymol: Greek rhyo-, from rhyax, stream of
lava. See also:liparite
Obsidian.
A rhyolite in which some grains or crystals are visibly larger than
others. Sinkankas
A phenomenon, observed in igneous rocks, in which different minerals
crystallize in concentric layers, giving rise to orbicular structure.
AGI
In this type driving, the drilling, loading, and blasting are carried out
in one shift and the mucking and transportation in the following one. This
enables every worker to specialize in his or her tasks and machines, which
in a highly mechanized job is a necessary condition for making the best
use of expensive equipment. It also reduces or eliminates the loss of time
for ventilation; in rhythmic driving it is carried out between two shifts.
Langefors
A regular interbanding of two or more types of sediment or sedimentary
rocks due to a regular change in the conditions of sedimentation, such as
alternation of wet and dry periods. See also:varved clay
The couplet of distinct types of sedimentary rock, or the graded sequence
of sediments, that form a unit bed or lamina in rhythmically bedded
deposits. It implies no limit as to thickness of bed, lamina, or
complexity, but the term should exclude groups of beds such as cyclothems
and carries no time or seasonal connotation. CF:cyclothem; varve.
AGI
a. The side of a pillar or the wall of an entry. BCI
b. The solid coal on the side of a gallery or longwall face; a pillar or
barrier of coal left for support.
c. The solid ore of a vein; an elongated pillar left to support the
hanging wall in working out a vein.
d. A stringer of ore in a lode.
e. The termination of a coal face. Where solid coal is left, the term fast
rib, end, or side, is used; and where the coal face ends at the gob, the
term used is loose rib, end, or side. TIME
f. See:buttock
g. A hard zone, bed, or horizon within a formation; a silicified zone in a
sedimentary stratum. Long
h. A ridge projecting above grade in the floor of a blasted area.
Nichols, 1
i. A ridge, paralleling the long axis of a drill string member, that acts
as a wear-resistant surface. Long
A crusher in which the material passes between a moving set of rolls with
ribs on their surfaces parallel to the axis of the rolls.
See also:roll
Enlarging a heading or drift.
a. One of a set of parallel bands or streaks in a mineral or rock, e.g.,
ribbon jasper; when the lines of contrast are on a larger scale, the term
banding is used. See also:stripe
b. Said of a vein having alternating streaks of ore with gangue or country
rock, or simply of varicolored ore minerals. CF:banded; book structure.
AGI
c. A color band in slate that represents original bedding and crosses the
superimposed slaty cleavage. Ribbon is generally undesirable and decreases
the value of the slate. Syn:pancake
A friction brake having a metal strap that encircles a wheel or drum and
may be drawn tightly against it. A band brake. Standard, 2; Fay
Geologic cross section drawn in perspective and joining control points
along a sinuous line. AGI
See:pillar boss
Dust found on the side walls of a mine. The dust from the roof is
generally included with this sample. Rice, 2
Final holes fired in blasting around sides of shaft or tunnel. Also called
trimmer. Pryor, 3